Only recently has it been realized that the pineal body may be a multipotential organ of internal secretion. Some express the view that the endocrine effects of the pineal may be explained on the basis of the primary target being rhythmic metabolic and transport mechanisms within the central nervous system. Certain high amphitude circadian rhythms within the pineal gland itself suggest an important role in relation to the biological clock. Modulation by the pineal of the neuroendocrine-reproductive axis is well documented and the possibility that an antigonadotropic hormone exists as a pineal secretory product is of paramount interest. The applicants have established methods for the purification of a substance from aqueous extracts of bovine pineal glands. The pineal antigonadotropin is postulated to be a small polypeptide. When injected into mice and rats this potential hormone retards puberty, reduces the weight of the gonads and accessory reproductive organs, inhibits fertility and blocks ovulation. In studies employing radioimmunoassays for gonadotropins, the pineal antigonadotropin has been observed to inhibit the postcastration rise in serum luteinizing hormone in male rats. We propose to continue work on the characterization of bovine pineal antigonadotropin using gel filtration, ultrafiltration, partition chromatography, ion exchange chromatography, thin layer chromatography, electrophoresis, preparative paper chromatography and quantitative amino acid analysis. A determination of the sequence (structure) of the compound will be undertaken and synthesis of the compound will be carried out in order that comparisons with the natural product can be made. Studies on the effects of the purified antigonadotropin on the development of puberty in immature animals, and others relating to the inhibition of ovulation in adult female rats, will be continued. Parallel ultrastructural studies on pineal secretion will be continued also, as well as the search for a site and mechanism of action of the antigonadotropin.